1. Field of the Invention
The invention relates to a heat treatment process for material bodies made of an iron-nickel superalloy, of the type IN 706. The invention also relates to heat-treated material bodies made of a high-temperature-resistant iron-nickel superalloy of the type IN 706, in particular for use in rotors of thermal machines.
2. Discussion of Background
The invention takes as its reference a prior art as described, for example, by J. H. Moll et al. "Heat Treatment of 706 Alloy for Optimum 1200.degree. F. Stress-Rupture Properties" Met. Trans. 1971, vol. 2, pp. 2153-2160.
It is known from this prior art that the properties of the alloy IN 706 which are critical for its use as a material for components which are subject to high temperatures, such as for example the heat resistance and the ductility, are determined by heat treatment processes which are carried out in a suitable manner. Depending on the microstructure of the starting body forged from the alloy IN 706, typical heat treatment processes comprise, for example, the following process steps: Solution annealing of the starting body at a temperature of 980.degree. C. for a period of 1 h, cooling of the solution-annealed starting body with air, precipitation hardening at a temperature of 840.degree. C. for a period of 3 h, cooling with air, precipitation hardening at a temperature of 720.degree. C. for a period of 8 h, cooling at a cooling rate of about 55.degree. C./h to 620.degree. C., precipitation hardening at a temperature of 620.degree. C. for a period of 8 h, and cooling with air, or, for example: Solution annealing of the starting body at temperatures of around 900.degree. C. for 1 h, cooling with air, precipitation hardening at 720.degree. C. for a period of 8 h, cooling at a cooling rate of about 55.degree. C./h to 620.degree. C., precipitation hardening at 620.degree. C. for 8 h, and cooling with air.